Pancreatic ß Cells Inhibit Glucagon Secretion from α Cells: An In Vitro Demonstration of α-ß Cell Interaction.

Interactions between endocrine α and ß cells are critical to their secretory function in vivo. The interactions are highly regulated, although yet to be fully understood. In this study, we aim to assess the impact of α and ß cell co-culture on hormone secretion. Mouse clonal cell lines α-TC6-1 (α cell line) and MIN-6 (ß cell line) were cultured independently or in combination in a medium containing 5.5, 11.1, or 25 mM glucose, respectively. After 72 h, hormone release was measured using insulin and glucagon secretion assays, the cell distribution was visualized by inverted microscopy and an immunocytochemistry assay, and changes in gene expressions were assessed using the RT-PCR technique. The co-culture of the two cell lines caused a decrease in glucagon secretion from α-TC1-6 cells, while no effect on insulin secretion from MIN-6 cells was revealed. Both types of cells were randomly scattered throughout the culture flask, unlike in mice islets in vivo where ß cells cluster in the core and α cells are localized at the periphery. During the α-ß cell co-culture, the gene expression of glucagon (Gcg) decreased significantly. We conclude that islet ß cells suppress glucagon secretion from α cells, apparently via direct cell-to-cell contact, of which the molecular mechanism needs further verification.

Taste alterations and oral discomfort in patients receiving chemotherapy.

PURPOSE: Taste alterations (TA) and oral discomfort in cancer patients are neglected side effects of the disease and treatments. They contribute to poor appetite, decrease food intake and affect quality of life, leading to adverse outcomes such as malnutrition and depression. The study aimed to explore TAs in relation to other oral conditions causing discomfort in cancer patients. Additionally, the correlation between patients' acidity of saliva and experienced TAs and oral discomfort was evaluated. METHODS: A case study including 100 patients diagnosed with cancer receiving chemotherapy or immunotherapy. Data were collected using two questionnaire forms: the Chemotherapy-induced Taste Alteration Scale (CiTAS) and an additional information questionnaire. Saliva samples were collected for each patient and measured with a pocket pH meter. Data were analysed using descriptive statistics, and comparisons were performed using the Kruskal-Wallis H test, Mann-Whitney U test and Fisher's exact test. RESULTS: The prevalence of reported TAs was 93%. Patient age, oral discomfort and swallowing difficulty were found to be significant factors for experienced TAs (p < 0.05). No correlation between patients' acidity of saliva and reported TAs and oral discomfort was found. CONCLUSION: CiTAS proved to be a convenient tool to collect information about TAs in cancer patients. Using the CiTAS tool, a high prevalence (93%) of reported TAs in cancer patients receiving chemo- or immunotherapy was found. CiTAS provides a fast and cheap recognition of symptoms and causes of TAs that can be addressed.

Steviol glucuronide, a metabolite of steviol glycosides, potently stimulates insulin secretion from isolated mouse islets: Studies in vitro.

AIMS: Steviol glycosides are the sweet components extracted from medicinal plant Stevia rebaudiana Bertoni, which have antihyperglycaemic effects. Steviol glucuronide (SVG) is the metabolite excreted in human urine after oral administration of steviol glycosides. We aimed to clarify whether SVG exerts direct insulin stimulation from pancreatic islets and to explore its mode of action. MATERIALS AND METHODS: Insulin secretion was measured after 60 minutes static incubation of isolated mouse islets with (a) 10-9-10-5 mol/L SVG at 16.7 mmol/L glucose and (b) 10-7 mol/L SVG at 3.3-16.7 mmol/L glucose. Islets were perifused with 3.3 or 16.7 mmol/L glucose in the presence or absence of 10-7 mol/L SVG. Gene transcription was measured after 72 hours incubation in the presence or absence of 10-7 mol/L SVG. RESULTS: SVG dose-dependently increased insulin secretion from mouse islets with 10-7 mol/L exerting the maximum effect in the presence of 16.7 mmol/L glucose (P < .001). The insulinotropic effect of SVG was critically dependent on the prevailing glucose concentration, and SVG (10-7 mol/L) enhanced insulin secretion at or above 11.1 mmol/L glucose (P < .001) and showed no effect at lower glucose concentrations. During perifusion of islets, SVG (10-7 mol/L) had a long-acting and apparently reversible insulinotropic effect in the presence of 16.7 mmol/L glucose (P < .05). Gene-transcript levels of B2m and Gcgr were markedly altered. CONCLUSION: This is the first report to demonstrate that SVG stimulates insulin secretion in a dose- and glucose-dependent manner from isolated mouse islets of Langerhans. SVG may be the main active metabolite after oral intake of steviol glycosides.

Effect of Steviol Glycosides on Human Health with Emphasis on Type 2 Diabetic Biomarkers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

The natural sweetener from Stevia rebaudiana Bertoni, steviol glycoside (SG), has been proposed to exhibit a range of antidiabetic properties. The objective of this systematic review was to critically evaluate evidence for the effectiveness of SGs on human health, particularly type 2 diabetic (T2D) biomarkers, collecting data from randomized controlled trials (RCTs). Electronic searches were performed in PubMed and EMBASE and the bibliography of retrieved full-texts was hand searched. Using the Cochrane criteria, the reporting quality of included studies was assessed. Seven studies, nine RCTs, including a total of 462 participants were included. A meta-analysis was performed to assess the effect of SGs on following outcomes: BMI, blood pressure (BP), fasting blood glucose (FBG), lipids, and glycated hemoglobin (HbA1c). The meta-analysis revealed an overall significant reduction in systolic BP in favour of SGs between SG and placebo, mean difference (MD): -6.32 mm Hg (-7.69 to 0.46). The overall effect of BMI, diastolic BP, FBG, total cholesterol, and high-density lipoprotein cholesterol (HDL-C) was a non-significant reduction in favour of SGs, and a non-significant increase in low-density lipoprotein cholesterol and triglyceride, while no significant effect of HbA1c was found. Heterogeneity was significant for several analyses. More studies investigating the effect of SGs on human health, particularly T2D biomarkers, are warranted.